In most cells, which structure forms the outer boundary of the cell and consists primarily of a lipid bilayer?

• A. Cytoskeleton
• B. Nuclear envelope
• C. Cell wall
• D. Plasma membrane

Answer: (D)

Verified step by step guidance

1. Identify the function of each structure listed: the cytoskeleton provides internal support and shape, the nuclear envelope surrounds the nucleus, the cell wall provides rigidity in plants and some other organisms, and the plasma membrane forms the boundary of the cell.
2. Recall that the plasma membrane is composed mainly of a lipid bilayer, which acts as a selective barrier controlling the movement of substances in and out of the cell.
3. Understand that the plasma membrane is present in all cells, including animal and plant cells, whereas the cell wall is only found in plants, fungi, and some prokaryotes.
4. Recognize that the plasma membrane's lipid bilayer structure is fundamental to its role as the outer boundary of the cell, maintaining the internal environment.
5. Conclude that among the options, the plasma membrane is the correct structure that forms the outer boundary of most cells and consists primarily of a lipid bilayer.